/Engine/Source/Editor/UnrealEd/Classes/Editor/UnrealEdEngine.h
Mark all selected actors and BSP models to be shown upon editor startup, by setting their bHiddenEd flag to false, if it not already. This directly modifies/dirties the relevant actors/BSP.
virtual void edactUnHideSelectedStartup ( [UWorld](API\Runtime\Engine\Engine\UWorld) * InWorld )